Plasticized butadiene polymer compositions containing phthalimidoalkyl alkanoates



Patented Aug. 5, 154 .1 2,425,233

UNITED STATES PATENT 0FFlCEl rnssrrcrzannu'ranmua mama comrosrrrous courammc rn'rrmmumo- ALKYLALKANOATES Nollrawing. Application January 8, 1945, I

- Stl'lll N0. 571,966 v s Claims. (01. see-st) Lil-hutadiene alone or copolymerized with other polymerizable monomers, which contain the polymerizable structure a 1 Thi invention relates to plasticized elastomer compositions and more particularly to such compositions in which so-called synthetic rubbers are i are excellent plasticizers for synthetic elastomers plasticized or softened with softening agents ofthe class of phthalimides of fatty acid esters. 4

In the manufacture and compounding ofrubher and synthetic rubber, it isnecessary to-brinlg the compound into a plastic state so that pigments, fillers, and the like can be incorporated therein. and so that the'product can be molded into the desired shape before vulcanlzing. In the case of natural rubber, simple heating by the friction of milling on a roller mill induces the necessary degree of plasticityforthese pi mses.

The so-called syntheticrubbers or synthetic elastomers on the othe'r="hand do not respond easily to milling treatment and often become hard and brittle or crumble when subjected to such milling. It is, therefore; essential to add to many of the synthetic elastomers softening or plasticizing agents to facilitate satisfactory milling and forming operations." c

It is desirable that .such softeners not only piasticize the elastomer, but that they shallnot seriously decrease the tensile strength and stretching capacities of the plasticized material.

I have found that phthalimides of fatty acid esters that is, the phthalimidoalkyl alkanoates,

and impart their beneficial softening properties without damage to the tensile strength and elongation characteristics of the resulting composition in many cases actually enhancing one or the other or both of these characteristics to some extent. 3

The imides utilizable assoftening agents inmy invention may be represented by the following structural formula l in which'R aim represent nemia-um or alkane-carbonyloxymethyl, Rrepresent's alkane' among which may be mentioned the aryl oleiines such as styreneand vinyl naphthalene; the alpha methylene carboxylic acids and thei esters,

nitriles and amides such as acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, methacrylonitrile, methacrylamide; isobutylene, methyl vinyl ether and so on. My softening agents are especially effective when utilized with v methyl-1i3-propanediol diacetate, and the like.

- The phthalimides described may be prepared, for example, by the following procedure: the calculated amount of phthalic anhydride for imide formation is added to an equivalent quantity of a primary amino hydroxy compound. and heated at about 150 to 180 C, for several hours-in adistillation apparatus until the calculated amount of water has distilled out. Then the equivalent amount of fatty aciddesired for esterification is added, and the mixture is again heated for several hours at about 150 to 180 C. until esterification is complete. The product is then recovered, for example, by vacuum distillation.

The amount of plasticizer utilized will vary with the relative difficulty of plasticization of the particular elastomer involved and with the degree ofsoftness' desired." In general, such softeners- -can be employed in a wide range of proportions, v and preferably within the range of concentra- 'tions varying from about ten to forty-five parts by weight. oi plasticizer for each 100 parts by wfei'glr tofelastomer. v I r I l, The plasticizers ,of my invention all-impart a high degree fof'plasticityof elastomer compositi -i s... it out se iously" reduc ng. the n le I strength snd'eloi seuon m ters;

s, "so lvenijent fmethod fofjevaluatihg the. "exfectiveness of plasticizing compositions comprises milling" the composition-in a'standard rubber for-. "mula on aconventional rubber mill, and then measuring the extrusion time at various pressures in an extrusion plastometer, for example. in an instrument and according to a method similar to that describe by J. H. Dillon in "Rubber. Chemistry and Technology," vol. 9, pp. 498-501 (July 1936). In order to evaluate the effect of the plasticizer on the tensile and elongation properties of the elastomer, samples of the sheet are tested for these factors in the standard Scott tensile tester. v.

As illustrative of my invention, tnesile, elongation, and extrusion values as, measured by the instruments above referred to, were run on several representative amides of the class described. The plasticizer was added in each case in the indicated amount to the standard formula given below, and milled into the stock in the conventional manner.

Test composition Parts by weight Hycar OR (butadiene-acrylonitrile copolymer) 100 Zinc oxide Stearic acid 1 Altax (benzothiazyl disulflde) Sulfur Carbon Aftermilling, partof each sample was Jected to tensile and elongation'tests, part was tested in the extrusion plastorneter with there- In the above table, a reduction in extrusion time indicates an increase in plasticity, that-is,

the more plastic the composition the more rapidly will it extrude, at a given pressure. vIt will be observed, that in every case the plasticiz- -ing effects are striking, and in one case this effect is superior to the'c'ontrols, dibutyl'phthalate and tricresyl phosphate, which are usually inconJunctlon with such tests for comparison.

It will also be observed,'that in general, the compositions show no loss in tensile and elongation over the original unplasticizedbatch, a considerable increase in these characteristics erally obtained.- U

While the above describes -thepr'efer'red embodimentg of my inventiomit is to be understood that departures may be made therefrom ,within the scope of the specification and claims.

What is claimed is:

1. A composition comprising a rubberlike synthetic elastomer of the class consisting of 1,3- butadiene polymers, and copolymers of butadiene I inwhichit and. R are' members the group consistingof hydrogen, alkyl and al- 4 and, as a softener therefor, a phthallmide of a fatty acid ester having the following structural formula o c R v W m in v in which R and R are members selected her-like 1,3-butadiene-acrylonitrile copolymer and, as a. softener therefor, a phthalimideof a fatty acid ester having the following structural formula selected from kanecarbonyloxymethyl and R represents alkanecarbonyloxymethyl.

3, A composition comprising a rubber-likesyn- 'thetlc ,elastometer of the clas consisting of 1,3-

butadiene polymers, and copoly'mers of butadiene polymerized with othertmonomers having the 4 polymerizable structure and, as softener therefor, "2-phthali'midoisobutyl acetate.

4. A composition'comprising a rubber-like syntheticelastomer of the classeonsistlngbf 1,3-

butadiene polymers, and copolyme'rs of butadiene polymerized with other monomers, having the polymerizable structure and, a softener therefor, i-phthalimidoisobutyl laurater 5. A composition comprising a rubberslike synthetic' elastomer of the class consisting of 1,3-

is n- Number polymerized with other monomers having the polymerizable structure} He -1C butadiene polymers, and copolymers of butadiene polymeri zable structure I n,c=c

polymerized with other monomers having the iandp-as asoftener therefor; 2-phthalimido-2- methyl-1,3-propanediol diacetate.

PHILIP F. TRYON.

REFERENCES CITED The following references are of record in the file of this patent: 1

UNITED s'rarss PATENTS Name Date Garvey. Aug. 3, i043 o'nma Ind. 8: :Eng. Chem".- article byqFisher, pages os -ssa'v l. 31, no. 3, August 1939.

from

' the groupconsistins of hydrogen. alkyl and al-' kanecarbonyloxymethyl, R is alkanecarbonyloxy- ,methyls 2. A composition of matter comprising a rub- 

